As a conventional technology to realize a high definition stereo image display, a green-color pixel shifting method as described in the following paragraph has been proposed. As for a stereoscopic viewing technology, polarizing glasses are well-known for a polarized dual-view stereo display to realize such stereo image display.
To begin with, a conventional display apparatus using the green-color pixel shifting method will be explained by using the FIG. 6. FIG. 6 shows a schematic that shows a display system 50 based on the technology used for the conventional display apparatus. The display system comprises an RB projection device 52, a dual G projection device 51 and a screen 43, where RB and G stand for red-color and blue-color lights and green-color light, respectively.
The RB projection device 52 is a projection device that comprises a lamp 31, a project lens 32 and an RB optical unit that projects R image and B image to a screen 43.
The dual G projection device 51 comprises lamps 31, projection lenses 32 and a dual G optical process unit 10 that projects a dual G image consisting of a G image and a pixel-shifted G image onto a screen 43.
The R image, G image (and the pixel-shifted G image) and B image respectively correspond to images of red-color, green-color and blue-color which are segregated for three primary colors by three display devices (or color panels)
The dual G optical process unit 10 will be explained by using the FIGS. 2, 6 and 7. FIG. 7 is a block diagram that shows a composition of a conventional dual G optical process unit 10. The conventional dual G optical process unit comprises a light source lamp 31 (shown in FIG. 6), G dichroic mirror 2 that filtrates the green-color light off a white light emitted by the light source lamp 31 penetrating therethrough, a polarizing beam splitter PBS 11 that segregates G light into two polarized beams as S wave and P wave as called G light-a and G light-b which are orthogonal to each other, PBS 5 and PBS 6 that reflect G light-a and G light-b into reflective liquid crystal devices 7 and 8, respectively, as well as the G light-a and G light-b traveling through the PBS 5 and PBS 6, two half-wave plates 12 and 13 being set in the path of G light-b, a polarized beam splitter PBS 14 that leads polarized two beams of G image lights (as G image light-a and G image light-b) into a projection lens 32. The polarized beam splitter as abbreviated as “PBS” allows the light being normally and parallely polarized against the surface of PBS to travel through and reflect upon the PBS, respectively. The dichroic mirror allows to filterate only the light that has a predetermined wave length to transmit therethrough.
The operation of this optical process unit is explained. A G light passes through G dichroic mirror 2 once a white light emitted from the light source lamp 31 is input thereto. The G light which is isotropically polarized is input to the PBS plate as PBS 11 and the P wave is reflected as G light-a and S wave is transmitted as G light-b. The behaviors of both G light-a and G light-b are explained as bellows.
(G Light-a)
The G light-a (P wave) that is reflected at the PBS plate PBS 11 is incident onto PBS 5 is reflected to a reflective liquid crystal device 7. The G light-a is reflected under the condition that the polarization is rotated 90 degrees at the reflective liquid crystal device 7. The polarized reflected G light-a works as an image light called as a G image light-a of which polarization is S wave. The G image light-a can travel through the PBS 5 and is incident to PBS 14 but transmits PBS 14 due to the polarization as S wave. Finally the G image light-a goes to a projection lens 32.
(G Light-b)
The G light-b (S wave) that transmits through PBS plate PBS 11 is incident onto a half-wave plate 12 and the polarization of G light-b is rotated. Then the G light-b (now P wave) that is incident to PBS 6 is reflected to a reflective liquid crystal device 8. The G light-b is reflected under the condition that the polarization is rotated 90 degrees in the reflection at the reflective liquid crystal device 8. The polarized reflected G light-b works as an image light called as a G image light-b of which polarization is S wave. The G image light-b passes through another half-wave plate 13 where the polarization is rotated in another 90 degrees and is incident to PBS 14 as P wave. Then the G light-b is reflected at PBS14 and finally goes to a projection lens 32.
In this system, a G image light and a pixel-shifted G image light are made from the G image light-a (S wave) and G image light-b (P wave), respectively. These two G image lights are projected onto the screen 43 with R image light (S wave) and B image light (S wave) which are projected by RB projection device 52. Then a high definition image display can be obtained.
As for the green-color pixel-shifted high definition image display has been proposed by a paper “A wide-screen projection of 4 k×8 k pixels” (Ref. 1).
A polarized dual-view stereo display is to realize such a stereo image display by the observer who uses polarized glasses that he or she sees two images by the right and left eyes where the two images have different polarizations provided by two display devices.
Reference:                Ref. 1; K. Hamada, M. Kanazawa, I. Kondoh, F. Okano, Y. Haino, M. Sato and K. Doi, “A wide-screen projector of 4 k×8 k pixels”, No. 46.3, Symposium of SID (Society for Information Display) (2002).        
In the conventional green color light pixel-shifted image display device, the normal image and the pixel-shifted image have different polarization (mutually orthogonal to the other) each other as P wave and S wave and are projected to the screen. In this polarization scheme, the polarization glasses to filtrate an image to the right-eye sight and left-eye sight that allows a stereo image viewing may pass either P wave or S wave of the pixel-shifted image or P wave rich or S wave rich image (of the pixel-shifted image) depending on the compliance to the alignment of the polarization of the polarizing glasses. Therefore, the composition of the total pixel-shifted image which is a mixture of the normal polarization image and orthogonal polarization image, each having the normal image component and the pixel-shifted image component, looses the balance between two image components upon the polarization of the polarizing glasses. In the projectors to project the image onto the screen of which image is viewed by the polarization glasses to produce stereo viewing image, the difference of the polarization may works as to select P wave or S wave, therefore the total pixel-shifted image looses the balance between the normal image component and the pixel-shifted image in the optical process for such projection. In other words, it is not possible to keep the compatibility between the G pixel-shifted image processing technology and the polarized stereo image processing technology since both processing uses the polarization technology.